Optical viewing instrument having negative lens and grid scale



Feb 14, 195a R. W. JUSTICE OPTICAL VIEWING INSTRUMENT HAVING NEGATIVELENS AND, GRID SCALE Filed April 16, 1946 INVENTOR- BY o ATTORNEYPatented Feb. 1 1950 U.NITED; .STAIE s oer-ice 1 DPTIEAL VIEWINGINSTRUMENT NEGATIVELENS AND' GR'ID SCALEJ v RichardW..lustice,"Be1vedere, Galifl.

A pplicationiiflpril 16;219.46;;Serial No. 662- 5815 xZtCIaimS.(cuss-:1)

This invention relates to optical instruments and more particularly toan optical sketching aid.

Amon the objects of the invention is the provision of an opticalinstrument through which the observer may view a landscape or othercombination of objects and obtain a proportional reduction of the vistaon an objective grid.

The invention is particularly advantageous to artists, militaryobservers and others, sketching a proportionally reduced reproduction ofan observed area.

Other objects and advantages will appear as the description progresses.In the specification and the accompanying drawings the invention isdisclosed in its presently preferred form. But it is to be understoodthat it is not limited to this form, because it may be embodied inmodifications within the spirit of the invention as defined in theclaims following the description.

In the one sheet of drawings:

Fig. 1 is a side elevation of an optical instrument constructed inaccordance with this invention, in collapsed condition.

Fig. 2 is a vertical section of the same in the extended or operativecondition, on the line ll-ll,Fig. 5.

Fig. 3 is a vertical section of the changeable marginal mask.

Fig. 4 is a front view of the instrument.

Fig. 5 is a rear View, looking through the reducing lens at the reducedfield of the grid.

Fig. 6 isa diagrammatic section of the focal field of the instrument.

Fig. 7 is a perspective view showing one method of using the invention.

In detail the structure illustrated in the drawings, referring first toFig. 2, comprises the tubular main body I, having the inturned flange 2,and the telescoping body 3 having the external flange 4 and telescopingwithin the main body.

The telescoping body has the rear wall 5 with the focal negative lens 6mounted in the axis thereof and held in position by the removable bezeli screwed or otherwise attached to the annular flange 8 within which theperimeter of the lens 6 is held by the bezel I.

The annular rim 9 is screwed or frictionally attached to the front edgeof the main body I. The transparent grid Ill overlies the front openinof the main body and is held in position by the flanged rim 9, and hasthe criss-cross proportional lines such as l2, l3 etched or printedthereon. It also has the horizontal and vertical focal-center indicatinglines l4, l5, bisecting the focal axisof the lens 8.

The field of vision is defined by the mask l6, mounted in the annularframe I! having the fiange l8, frictionally telescoping over the flangedrim 9. This mask has a field of vision defined by the vertical andhorizontal marginal edges I9, 20, surrounding an opening that may be ofthe desired size and shape. It is proposed to have several of such maskswith various sized openings, as accessories for use in conjunction withthe body I. The first image entering at Fig. 4, is reduced by the lens 6and appears as in Fig. 5. If the mask is composed of transparent plasticor the like, the opening may be omitted and the margin 19, 20 defined byan opaque overlay on the grid [0.

The formula of the lens 6 is substantially as follows: Any object atinfinity comes to the sharp focus at F. The distance from F to A is aconstant property of the particular lens used and depends upon thedesign of the lens.

The grid it appears at the plane C. Objects such as D on any planebetween infinity and the grid !0 appear in planes such as E, between Fand C, which is a relatively short distance.

The eye at G, due to its depth of field, is able to focus simultaneouslyand comfortably on all planes between F and C, when the instrument isheld about twelve inches from the eye, which is relatively a longdistance, and may be varied to suit the vision of the individual user,by the distance it is held from the eye.

In field sketching, as in Fig. 7, the instrument I may be attached tothe sketchboard or easel X by a bracket such as Y, for the convenienceof the user, who then has both hands free, with the instrument I in lineof vision.

The grid mesh l2, l3 may be coarser or finer than shown, and the areaand shape of the mask may be varied to suit various conditions in theuse of the invention. And the size of the image may be varied bysubstitution of lenses of the desired focal value for the lens 6.

For greater accuracy the sketching surface as in Fig. 7, may becriss-crossed with lines corresponding to the grid area It).

Having fully described this invention and its mode of operation, what Iclaim and desire to secure by Letters Patent is:

1. An optical instrument in the class described. comprising atelescoping body having a reduced aperture in one end; a negative lensmounted in and closing said aperture; a transparent closurein theopposite larger end of said body and having'visible grid lines disposedupon its surface said grid lines being positioned a distancesubstantially equal to the focal length of said negative lens away fromsaid lens, so that the area of said grid lines appears in a reducedscale on the area of said lens.

2. An optical instrument in the class described, comprising atelescoping body having a reduced aperture in one end; a negative lensmounted in and closing said aperture; a transparent closure in theopposite larger end of said body and having visible grid lines disposedupon its surface said grid lines bein positioned a distancesubstantially equal to the focal length of said negative lens away fromsaid lens, so that the area of said grid lines appears in a reducedscale on the area of said lens; and a removable mask detachably attachedto the said larger end of the body and having an aperture therethroughfor outlining a restricted area of the grid lines on said transparentclosure.

RICHARD W. JUSTICE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 666,415 Fall Jan. 22, 1901761,033 Cross May 24, 1904 926,912 Vogt et a1 July 6, 1909 1,085,048Hukill Jan. 20, 1914 1,298,648 Birault Apr. 1, 1919 1,415,833 GinsburgMay 9, 1922 1,461,063 Lichtman July 10, 1923 1,616,723 Wandersleb Feb.8, 1927 1,760,792 Stenz May 27, 1930 2,240,931 Hurd May 6, 19412,285,498 David June 9, 1942

